Inspired by the nature, scientists have gone so far in the technology of concrete. Concrete is the most important building material for the construction but with time it develops cracks these small cracks makes the whole structure vulnerable because water seeps into degrade the concrete and corrode the steel reinforcement and thus reducing the life span. With innovation in science civil engineers have now made it possible to make self-healing concrete.
How does Bio-Concrete Works?
Self-Healing concrete is the concrete that will biologically produce limestone to heal the small cracks that appear on the surface of the concrete. Generally, selected type of bacteria Genus Bacillus, along with calcium based nutrients known as lactate, nitrogen and phosphorous are added to ingredient of concrete.
These agents can lie dormant within the concrete upto 200 years. The spores of bacteria germinate on the contact with water and nutrients. After the activation, bacteria start to feed on the calcium lactate and then the lactate is converted into insoluble limestone and thereby healing it up. It is just like a human bone is healing on its own like a living body. Oxygen is an essential element required for the corrosion of steel and all this oxygen is consumed by the bacterial activity, thus leaving the steel more durable in reinforced concrete. The two self-healing parts (bacterial spore and calcium lactate) are introduced to concrete within separate expanded clay pellets 2-4mm wide which ensure that the agents will not be activated during the cement mixing process.
Finding the Right Bacteria: -
Cement and water have a pH value up to 13 make hostile environment for life. It was found after the research that group of bacteria that produced spores and had thick walls were able to survive.
Interests from industry: -
When the idea of bacteria mediated concrete was mooted in 1900s, there was lack of interest from commercial engineering. Sectors for such products. Now products are being developed for tunnel lining, structural basement walls, highway bridges, concrete floors and marine structures.
The first issue is that the clay pellets holding the self-healing agent comprise 20% of the volume of the concrete. The clay is much weaker than the normal aggregate by 25% and thereby reducing its compressive strength.
The second issue is that its cost is almost double that of conventional concrete.